A major multiday, multiagency law enforcement operation targeting large marijuana farms in the heart of the pot-rich Emerald Triangle has uncovered serious environmental damage along with huge numbers of pot plants, according to a state Fish and Wildlife officer participating in the operation.

“So far, what we’ve seen are numerous stream bed alterations” created for the purpose of watering pot plants, said state Fish and Wildlife Lt. Chris Stoots, a member of the department’s Watershed Enforcement Team. The actual numbers will be revealed at a Friday news conference, he said.

He said most of the dozen, or so, cannabis gardens he’s visited since the operation began Monday contained thousands of plants each and he thinks people will be surprised when the totals are tallied and made public.

“I don’t think there were any properties we went to with under 1,000 plants,” Stoots said.

Humboldt County sheriff’s spokesman Lt. Wayne Hanson said Wednesday his department served four search warrants during the first two days and seized about 15,300 plants. Mendocino and Trinity sheriff’s officials have not reported the number of plants they seized nor the number of search warrants served. The Mendocino County Sheriff’s Office said it would not disclose details of the raids until the Ukiah news conference on Friday afternoon.

The raids are taking place in the Island Mountain area, where Mendocino, Humboldt and Trinity counties meet. Participants include law enforcement officers from the three counties and Fish and Wildlife.

This week’s eradication operation is focused on individual private properties where pot farmers are growing outside of legal limits, Hanson has said.

The Humboldt County search warrants include marijuana grown in greenhouses near residences, he said.

People familiar with the remote area said much of it has been subdivided into 40- to 160-acre parcels.

Stoots said it appears that many of the people were there for the sole purpose of growing marijuana. He saw a number of residences built of plywood.

They “basically just set up makeshift housing in order to have a residence while farming,” Stoots said.

Most of the sites raided have some amount of environmental damage, he said. It includes unpermitted grading; the use of fertilizers and herbicides in a way that allows them to be washed into streams; and water diversions, including the damming of streams.

Cannabis is a thirsty plant. In a report on watersheds and marijuana released last year, Fish and Wildlife researchers’ conservatively estimated each plant uses 6 gallons a day. Some marijuana advocates say much less can be used, but others, including Tim Blake, founder of the North Coast’s Emerald Cup cannabis competition, has said mature, tree-sized plants need closer to 15 gallons a day.

Environmentalists and scientists are worried about the water use.

Just the illegal marijuana plants confiscated in California by law enforcement in recent years — between 2 million and 4 million annually — use upward of 1.8 billion gallons, or about 600,000 water tanker trucks over their five-month growing season, based on the average water usage documented in the study.

It’s enough to stanch the seasonal flow of many small creeks in the region, potentially stranding the young salmon and steelhead that already are threatened or endangered.

Stoots said he doesn’t believe there are significant fish populations in the seasonal creeks that he saw being diverted and dammed. But the creeks normally would feed a nearby branch of the Eel River where fish do dwell and which already is running low.

It appeared some of the growers subjected to this week’s raids were making an effort to limit their damage to the environment, but their diversions still were illegal, Stoots said. Others showed “a complete disregard for the damage they were causing,” he said.

Area cannabis proponents reached Wednesday for comment said they don’t know any of the people whose gardens were raided and have only secondhand knowledge of is occurring on and around Island Mountain.

But they voiced dismay over the law enforcement raids, which they say hampers efforts of growers, regulators and law enforcement to work together to solve marijuana-related regulatory issues.

“There are tremendous environmental and public safety issues associated with unregulated cannabis cultivation. Solving these problems will require a broad coalition of stakeholders, including some of the very farmers being targeted right now. This “business as usual law enforcement” will be just as ineffective now as it has been for decades,” said Hezekiah Allen, executive director of the Emerald Growers Association.

You can reach Staff Writer Glenda Anderson at 462-6473 or glenda.anderson@pressdemocrat.com. On Twitter @MendoReporter